GB2491147A - Fuel injection system comprising fuel injectors linked in series - Google Patents

Abstract

Disclosed is a fuel injection system comprising at least one fuel injector 20, 30, 40, 50 which has an outlet that leads to the inlet of another fuel injector 30, 40, 50. The fuel injectors are connected in series via high pressure fuel lines 23, 33, 43. Each fuel injector 20, 30, 40 has a high-pressure fuel inlet 21, 31, 41 which splits into a fuel supply paths for the injector itself and for an outlet 22, 32, 42 to the next injector 30, 40, 50 in the series. Such an arrangement is used in place of a common rail injector thus cutting down on the cost of parts and weight of the fuel injection system as a whole. Also disclosed is a fuel injector comprising a high-pressure fuel inlet 21 connected to a high-pressure fuel outlet 22 of the injector and a branch point 82. One route of the branch point leads to a fuel dispensing nozzle 64 via a dispensing passageway 62 whilst another route leads to a pressure control chamber 76.

Description

Fuel Injection System The present invention relates to a fuel injection system for an internal combustion engine, especially for automotive applications.

Existing fuel injection systems employ a common fuel supply rail which supplies pressurised fuel via respective outlets to a plurality of fuel injectors. Each injector has a valve which is actuated to admit fuel via a single high pressure connection into a respective combustion chamber.

The provision of a common fuel supply rail as a separate component involves additional expense in the manufacture of a fuel supply system. The weight of the supply rail and its associated supporting brackets is also a factor to be taken into account.

Aspects of the present invention seek to at least partially overcome one or more of the above disadvantages.

According to the present invention there is provided a fuel injection system comprising a pressurised fuel source connected to a fuel inlet of a first fuel injector characterised in that the first fuel injector has a fuel outlet which is connected to a fuel inlet of at least one further fuel injector.

This has the advantage of avoiding the need for a common fuel supply rail.

Preferably, the fuel inlet of at least the first fuel injector branches into first and second high-pressure conduits, the first conduit constituting said fuel outlet. Such an arrangement ensures that fuel at a high pressure is available for the next fuel injector which is not subject to pressure variations.

In preferred embodiments the second conduit branches into third and fourth conduits, the third conduit supplying fuel to a control chamber for operating a fuel-dispensing nozzle of the injector and the fourth conduit supplying fuel to a fluid dispensing passageway connected to said nozzle. Throttle orifices may be provided in the third and fourth conduits, so that fuel is supplied at suitable lower pressures to the control chamber and to the fuel dispensing passageway.

The fuel dispensing passageway is kept filled with fuel to reduce or avoid supply pressure variations in the supply to the nozzle and has a volume within the range 2 to 5cc, preferably 3 to 4cc. The throttle orifice in the fourth conduit also serves to reduce pressure variations.

The system preferably comprises at least four fuel injectors, wherein the fuel outlet of the first fuel injector is connected to a fuel inlet of a second fuel injector, the second fuel injector having a fuel outlet which is connected to a fuel inlet of a third fuel injector, and the third fuel injector having a fuel outlet which is connected to a fuel inlet of a fourth fuel injector.

According to a second aspect of the present invention, there is provided a fuel injector comprising a high-pressure fuel inlet connection which is connected to a branching point with a first outlet connection to a fuel dispensing passageway to a fuel-dispensing nozzle and a second outlet connection to a control chamber, the pressure in which is arranged to control operation of the nozzle, characterised in that upstream of the branching point there is disposed an additional branching point to which is connected a high-pressure fuel outlet of the injector.

A preferred embodiment of the present invention will now be described, by way of example only, with reference to the accompanying drawings of which: Figure 1 is a schematic top plan view of a fuel injection system in accordance with the present invention; and Figure 2 is a schematic side view of a multiport fuel injector of the fuel system of Figure 1.

Referring to the drawings, Figure 1 shows a fuel injection system 10 for an automotive engine. The system comprises a pump 12 incorporating a pressure limiting valve (not shown) and a pressure sensor (not shown) . Fuel at a high pressure is supplied by the pump to a fuel inlet 21 of a first fuel injector 20. A fuel outlet 22 of injector 20 is connected via a high-pressure pipe 23 to a fuel inlet 31 of a second fuel injector 30. A fuel outlet 32 of injector 30 is connected via a high-pressure pipe 33 to a fuel inlet 41 of a third fuel injector 40. A fuel outlet 42 of injector 40 is connected via a high-pressure pipe 43 to a fuel inlet 51 of a fourth fuel injector 50.

Figure 2 shows a side view of the first fuel injector 20.

Injector 20 is a so-called mini-rail injector in which a mini-rail passageway 62 is provided to contain a volume, in effect a small reservoir, of fuel to avoid pressure oscillations. The volume of the passageway lies within the range 2 to 5cc and typically lies in the range 3 to 4cc. The nozzle needle 64 and valve piston 66 are produced as one integral part. The injector is actuated by a solenoid valve 68.

Fuel inlet 21 receives high pressure fuel from the pump 12 and feeds it to a junction or node 72. Here the fuel flow is divided into two streams still at high pressure.

A first of the fuel streams is supplied via outlet 22 to pipe 23 connected to the inlet of the second injector 30.

Fuel in the second stream from node 72 flows to a second node 82 where it is separated into two streams, namely a first stream used for injection and a second stream solely for activating the valve needle 64. Fuel in the first stream is supplied to the mini-rail passageway 62 to keep it full of fuel. Passageway 62 is preceded by a throttle 70 comprising a calibrated orifice.

Fuel in the second stream from second node 82 flows through a throttle 74. Here the pressure of the fuel is reduced from high pressure to medium pressure. The fuel then enters a control chamber 76, whereby the pressure it exerts on piston 66 causes needle 64 to selectively open and close the nozzle. The fuel leaves the control chamber 76 via a further throttle 78 after which it is a substantially ambient pressure. From there the fuel returns to the vehicle fuel tank (not shown) via a low pressure rubber backleak line 80. The lines 80 from the four fuel injectors are connected together so that a common line supplies fuel to the tank.

Fuel injectors 30 and 40 are of identical construction to injector 20. The outlet 32 of the injector 30 is connected to the inlet 41 of injector 40 and so on. Fuel injector 50 is of similar construction, but does not have an outlet.

The above-described system has numerous advantages. By using high-pressure pipes 23, 33, 43 to interconnect the fuel injectors, the need for a common rail is avoided.

This leads to a net weight saving of approximately 2kg.

The reduction of vibrating masses leads to a decrease in vibrational stress.

The throttle 70 for each injector is located in the respective feed channel in a location downstream of the connection between the fuel inlet 21 and the fuel outlet 22 of the injector; accordingly the throttle does not have any undesired influences on the inlet pressure of the following injector.

The throttles have the advantage of damping variations in pressure, in particular in combination with the capacity of the associated mini-rail passageway.

Various modifications can be made to the above-described system, for example, a pressure sensor nay be incorporated in the solenoid of each injector. These pressure sensors may replace or supplement the pressure sensor incorporated in the pump 12.

The injectors may be of any suitable type. There may be any desired number of injectors in the chain.

Instead of being combined, the lines 80 may be individually connected to the vehicle fuel tank. Instead of being connected to the vehicle fuel tank, the lines 80 may be connected to another fuel reservoir.

Reference Numerals Fuel injection system 10 Pump 12 Fuel injectors 20, 30, 40, 50 Fuel inlets 21, 31, 41, 51 Fuel outlets 22, 32, 42 Pipes 23, 33, 43 Passageway 62 Nozzle needle 64 Piston 66 Solenoid valve 68 Throttles 70, 74, 78 Nodes 72, 82 Control chamber 76 Line 80